Many studies have conventionally been made to reduce fuel consumption by reducing rolling resistance (expressed also as “by improving rolling resistance performance”) of tires. Further reduction in fuel consumption of automobiles has been more and more strongly required in recent years, and a rubber composition for a tread among various tire components, which occupies a large portion of a tire, is required to be more excellent in low heat build-up property.
Known as a method for sufficiently improving low heat build-up property of a rubber composition is a method in which the amount of a reinforcing filler in the rubber composition is reduced. In this case, however, hardness of the rubber composition decreases and thereby the tires obtained are softened, which disadvantageously causes decrease in handling performance (handling stability) and wet grip performance of automobile and causes decrease in abrasion resistance of tires.
Patent Document 1 discloses a rubber composition for tires which contains both anhydrous silica and hydrous silica in order to improve wet skid resistance. However, there remains a problem that low heat build-up property cannot be sufficiently improved.
Patent Document 2 discloses a modified diene rubber composition inclusive of silica and a diene rubber modified with an organosilicon compound, and excellent in rolling resistance performance (fuel economy performance), grip property, and abrasion resistance. Patent Document 3 discloses a rubber composition inclusive of a tin-modified polybutadiene rubber and excellent in cut resistance, fuel economy, and the like. However, the rubber compositions can be further improved to achieve both lower heat build-up property and better wet grip performance.
Patent Document 1: JP-A 2003-192842
Patent Document 2: JP-A 2000-344955
Patent Document 3: JP-A 2006-063143